Gasifiers produce gaseous fuel that may be used in engines (for example, internal combustion engines that may be used to produce electricity and/or power vehicles) from carbonaceous material (for example, biomass and organic waste). Gasifiers conventionally use a combination of the following four reactions: combustion, reduction, pyrolysis, and drying. Fixed bed gasifiers (or “moving bed” gasifiers) are typically arranged as either an updraft gasifier type or a downdraft gasifier type. The updraft gasifier type utilizes the heat from the gas rising up from the combustion process to reduce, pyrolyze, and dry the carbonaceous material. As shown in FIG. 1, this allows for beneficial heat transfer between the processes (from high temperature reactions to lower temperature reactions). However, because the output gas goes through the pyrolyzing and drying processes last, the gas is relatively unclean and may include volatile tar gases and particulates that must be filtered and prepared before use. The downdraft gasifier type, however, dries the carbonaceous material, pyrolyzes the dried carbonaceous material into tar gas and charcoal, combusts the volatile tar gas, and finally reduces the combusted tar gas with the charcoal, thus producing relatively cleaner gaseous fuel than the updraft gasifier type. This may facilitate use of the gaseous fuel in the engine. However, the thermal and chemical relationships between successive stages in the downdraft gasifier are less than ideal for efficiency. For example, as shown in FIG. 2, heat is necessary to dry the carbonacecous material, but there is no obvious source of heat from within the downdraft gasification process. Similarly, pyrolysis occurs after drying, but the ideal temperature for pyrolysis is higher than that of drying, also necessitating heat input. Similarly, combustion occurs after pyrolysis, but the ideal temperature for combustion is higher than pyrolysis, again necessitating heat input. Also, in downdraft gasifiers where the processes are not adequately separated, higher temperature processes become parasitic loads on lower temperature processes, decreasing the effectiveness of the gasifier in converting carbonaceous material into gaseous fuel. For example, the drying process may become a parasitic load on the pyrolysis process, decreasing the effectiveness of the carbonaceous material to tar gas/charcoal conversion in the pyrolysis process and/or the pyrolysis process becomes a parasitic load on the combustion and/or reduction processes, decreasing the conversion effectiveness in the combustion and/or reduction processes. Additionally, gaseous fuel output from the reduction process is typically too hot to be used in an engine, and must be cooled. Also, any water content of the carbonaceous material is preferably substantially fully removed in the drying process to remove the thermal load of heating water in the pyrolysis and combustion processes. However, additional water may be beneficial in the reduction process, which occurs after the pyrolysis and combustion processes. While a downdraft gasifier may benefit from heat sources and material transporters in order to maintain the gasification process, the use of an external heat source and/or not effectively managing materials within the system will significantly decrease the effective carbonaceous material to gaseous fuel conversion of a downdraft gasifier and may decrease the viability of using the downdraft gasifier as an alternative energy source. Prior attempts in heat management within downdraft gasifiers (for example, using waste heat from one process to heat another) have also been substantially complicated, included many components, and expensive. Thus, there is a need in the downdraft gasifier field to create an improved system and method for heat and material management within a downdraft gasifier.